stat.bay.est {sma} | R Documentation |

## Calculates an Odds Ratio for Each Gene in a Multi-slide Microarray Experiment.

### Description

This function takes independent, sufficient estimates of
the effect and its variance for each gene in a multi-slide microarray experiment
and returns an odds ratio for each gene: log( Pr(the gene is
differentially expressed) / Pr(the gene is not differentially expressed)
). The parameter estimates of the Bayesian model used, as well as some
data structures which are useful when presenting the lodscore
graphically are also in the output.

### Usage

stat.bay.est(M=NULL, Xprep=NULL, para=list(p = 0.01, v = NULL, a = NULL, c = NULL))

### Arguments

`M` |
Matrix of (normalized) log expression ratios
*M = log_2 (R/G)* (E.g. output from stat.ma()) |

`Xprep` |
A list containing the effect estimates and variances for
the genes, as well as some constants needed for the odds ratio |

`para` |
Estimates of the parameters used in the Bayesian
calculations. (These are calculated only if not
already supplied as input. See details!) |

### Details

Xprep and para are optional input, but they are always in the
output. If Xprep is supplied as input, M is unnecessary
input. If Xprep is not supplied, stat.bay.est assumes the experiment
consists of ncol(M) microarray slides all measuring the same effect
(which will be stimated by Mbar). A subset of the parameters in para can be specified in the
input, allowing the function to estimate only the others.

Xprep is a list containing

Mbareffect estimates for all genes (#genes x 1)
Vestestimates of sigma^2 (effect variances) for all genes (#genes x 1)
kconstant so that Mbar~N(.,sigma^2/k) for all genes (1 x 1)
fdegrees of freedom for Vest (1 x 1)
para is a list of parameters common to all genes containing

pProbability that a random gene is differentially
expressed. Default is 0.01.
v,aParameters in the prior for the variance such that a*k/(2*sigma^2) ~Gamma(v,1)
cParameter in the prior for the mean expression ratio.
### Value

A list of

`Xprep` |
Some data structures useful in graphical
presentation. See details! |

`para` |
Estimates of the parameters used in the Bayesian
calculations. See details! |

`lods` |
The log odds ratio for each gene. |

### Author(s)

Ingrid Lönnstedt ingrid@math.uu.se

### References

I. Lönnstedt and T. P. Speed. Replicated Microarray Data.
Statistical Sinica, Accepted, see http://www.stat.berkeley.edu/users/terry/zarray/Html/papersindex.html

### See Also

`stat.bayesian`

,`plot.bayesian`

### Examples

data(MouseArray)
## mouse.setup <- init.grid()
## mouse.data <- init.data() ## see \emph{init.data}
## mouse.lratio <- stat.ma(mouse.data, mouse.setup)
mouse.bayesian<-stat.bay.est(M=mouse.lratio$M)
plot(mouse.bayesian$Xprep$Mbar, mouse.bayesian$lods)
#alternatively
mouse.est<-apply(mouse.lratio$M,1,mean.na)
mouse.Vest<-apply(mouse.lratio$M,1,var.na)
n<-ncol(mouse.lratio$M)
k<-n
f<-n-1
mouse.Xprep<-list(Mbar=mouse.est,Vest=mouse.Vest,k=k,f=f)
mouse.bayest<-stat.bay.est(Xprep=mouse.Xprep)
plot(mouse.bayest$Xprep$Mbar, mouse.bayest$lods)

[Package

*sma* version 0.5.15

Index]